Spinel vs Amethyst
Spinel is harder (Mohs 8) than Amethyst (Mohs 7), so it resists scratching better.
Spinel has the higher refractive index (1.718 vs 1.544–1.553), which a refractometer can use to separate them.
Spinel is denser (SG 3.6 vs 2.65); a spinel of the same size weighs about 36% more.
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| Property | Spinel | Amethyst |
|---|---|---|
| Species / material | Spinel | Quartz |
| Mohs hardness | 8 | 7 |
| Refractive index | 1.718 | 1.544–1.553 |
| Specific gravity | 3.6 | 2.65 |
| Crystal system | Cubic | Trigonal |
| Birefringence | None (isotropic) | 0.009 |
Values are typical ranges from standard gemmological references; individual stones can vary.
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